The automatic fabrication of glass articles is carried out by means of glass forming machines such as those of multiple sections known as I.S. glassware forming machines, or the rotatory type known as Lynch and through forming processes known as blow and blow, press and blow or press.
For the manufacture of glassware articles, it is necessary to feed molten glass gobs towards the machine. The mentioned molten glass gobs are obtained from a feeder that is a part of a glass melting furnace.
A molten glass feeder generally includes a feeder bowl defining an outlet spout; a plate having feeding orifices is placed adjacent to said spout, through which flows a discharge of molten glass; a rotating tube in the bowl perpendicularly aligned with the spout, is mounted on a mechanism that controls its rotation and height with respect to said spout in order to homogenize the glass in said feeder bowl and regulate the passage of the glass towards the orifice; a reciprocating plunger into the tube and aligned with the orifice and which is mounted on a reciprocating mechanism which imparts and controls its reciprocating run in order to push out a predetermined amount of glass towards the orifice; and a pair of reciprocating shear blades opposite to each other, placed under the orifice, and mounted on their respective reciprocating mechanisms in order to cut off the glass gobs from the flow of glass that comes out of the orifice.
Regularly said tube is the element which controls the amount of glass that should come out from the orifice and which is to be cut off by means of the shear blades in order to provide the glass gobs having the required weight to manufacture an article of predetermined weight.
However, the real weight similar to the predetermined weight is not always achieved because of disarrangements in the height of the tube which affect the weight of the gobs and of the articles.
In order to achieve a control on the weight of the glass gobs and of the finished articles the U.S. Pat. No. 2,306,789 of W. L. Mc. Namara describes an automatic electromechanical regulator used to control the weight of the gobs, which includes a scale to weigh the finished articles, which provides a representative signal of the weight to elements which respond to the same and which operate an electric motor that is connected to the tube mechanism in order to regulate the height of the tube with respect to the orifice.
After the aforementioned patent a series of mechanisms appeared in order to control the height of the tube, such as those described by the U.S. Pat. Nos. 2,479,121 of M. K. Koleda, 3,239,326 of R. E. Tyner and 3,874,866 of Iacovazzi et al, as well as diverse forms for weighting the finished articles or the glass gobs, such as those described by the U.S. Pat. Nos. 3,846,107 of T. V. Foster et al. 4,339,028 of T. Meacle and 4,165,975 of Kwiatkowsk et al.
Trying to achieve a more precise control on the weight of the gobs and the articles, other control systems arouse which detect the volume of the gob through several form detecting chambers, placed at 90 degrees to each other such as the one described by the U.S. Pat. No. 4,205,973 of W. H. Ryan.
However, even though a better control of the height of the tube by means of measuring its weight or volume is already had, there still subsists the problems about lack of adjustment in the weight of the gob. The latter is so because, up to now, there was no knowledge about the dynamic process of the system that includes the tube movement nor this had been taken into account. The mentioned movement introduced a strong tendency to unstably the control of the system.
The latter permitted the inventor of the present invention to determine that the conditions which upset the desired weight of the glass gobs are the following:
1. The temperature, homogeneity and viscosity of the molten glass;
2. The level of the glass in the feeder bowl which exerts a load on the orifice zone;
3. The wear of the orifice through which the glass flow comes out; and
4. The disarrangements in the tube mechanism.
Having thus determined the variables that affect the system, the inventor of the present invention designed an electronic system in order to automatically control the weight of the glass gobs, in which through the continuous monitoring of the weight of the finished articles, of the height of the tube with respect to the orifice and of the temperature and level of the glass in the feeder bowl, through adequate detectors, and by means of a data processor which compares the real weight of the articles with the predetermined weight of the same, and relates the weight deviations with the height of the tube and the temperature and level of the glass in the feeder bowl, provides a compensation for variations in the height of the tube in order to permit the adequate passage of glass between the mentioned tube and the orifice achieving in this wax the predetermined weight for the articles.